Electronic musical instrument with a pseudorandom pulse sequence generator

ABSTRACT

Apparatus for producing complex rhythm patterns (rhythm &#39;&#39;&#39;&#39;breaks&#39;&#39;&#39;&#39;) involving operation of a plurality of percussion devices in a pseudorandom manner. A clock pulse generator drives a pseudorandom pulse sequence generator having a large number of outputs on which appear a large number of different combinations of output pulses. Each clock pulse effects a change in the combination of pulses appearing at the outputs. The outputs of the pseudorandom pulse sequence generator are combined in logic gates having outputs connected to a plurality of percussion devices which are operated in pseudorandom manner (depending on the output pulse combination) at a tempo determined by the source of clock pulses. The source of clock pulses may be a free-running clock pulse generator operating at any desired one of various rates or may be derived from a musical instrument, e.g. an organ, so that the clock pulse rate (rhythm) is set by the player of the instrument.

United States Patent [72] Inventors James K. Miller;

Theodore II. Shepertycki, both 01 Ottawa, Ontario, Canada [21] Appl. No.831,641 [22] Filed June 9, 1969 [45] Patented Dec. 21, 1971 [73]Assignee Canadian Patents and Development Limited Ottawa, Ontario,Canada [54] ELECTRONIC MUSICAL INSTRUMENT WITH A PSEUDORANDOM PULSESEQUENCE GENERATOR 3 Claims, 7 Drawing Figs.

[52] 11.8. C1 84/1.03, 84/ 1 .26 [51] lnt.Cl Gl0h 1/02 [50] Field ofSearch 84/1.01, 1.03, 1.26, DIG. 12

[56] References Cited UNITED STATES PATENTS 13226921 2/1969 Park 84/1.033,358,068 12/1967 Campbell 84/1.01 3,482,027 12/1969 Okamoto et al.134/1 .03

Primary Examiner-D. F. Duggan Assistant Examiner-Stanley .l WitkowskiAttorney-Smart and Biggar ABSTRACT: Apparatus for producing complexrhythm patterns (rhythm breaks") involving operation of a plurality ofpercussion devices in a pseudorandom manner. A clock pulse generatordrives a pseudorandom pulse sequence generator having a large number ofoutputs on which appear a large number of different combinations ofoutput pulses. Each clock pulse effects a change in the combination ofpulses appearing at the outputs. The outputs of the pseudorundom pulsesequence generator are combined in logic gates having outputs connectedto a plurality of percussion devices which are operated in pseudorandommanner (depending on the output pulse combination) at a tempo determinedby the source of clock pulses. The source of clock pulses may be afreerunning clock pulse generator operating at any desired one ofvarious rates or may be derived from a musical instrument, e.g. anorgan, so that the clock pulse rate (rhythm) is set by the player of theinstrument.

EXCLUSIVE on CIRCUIL 4o J on: or 10 UNIT osuws (FLlP-FLOPS) CLOCK if 0 2L 3 4 5 s 1 e s H reusnces 0-9 0 o 2 3 4 5 s 1 a 9 lo HOUTPUTS/ m O-IO)Q I 1 OUTPUT 2s OUTPUT 2| OUTPUT 17 ONE POSSIBLE FORM OF PSEUDO-RANDOMSEQUENCE GENERATOR SHOWING 14 OF 1023 POSSIBLE OUTPUTS TO DRIVEPERCUSSION PATENTEU 05221 197i 3.629.482

SHEET 1 OF 3 Y PERFORMER ,0 ,3

SOUND r OUTPUT MUSICAL //5 J6 INSTRUMENT RHYTHM SOUND BOX PERCUSSION(PSEUDO OUTPUT RANDOM) /4 l6 P SEUDO- BOX SION UTPUT D MUSICAL SOUNDPERFORME INSTRUMENT OUT 2 l4 PSEUDO- 5... SOURCE RANDOM To OF PULSE 1*CLOCK SEQUENCE 5$P g PULSES GENERATOR 20 2/ 23 PULSE PULSE SOURCECOMPARISON ON CIRCUITRY MUS'CAL INSTRUMENT F/GJ INVENTORS JAMES K.PULFER THEODORE H.SHEPERTYCKI AT ORNEYS PATENTED UECZI I971 SHEET 3 BF 3PERCUS N IHIIIH DEVIC 2a g L D GIQ PERCUSSION RHYTHM W0 DEVICE [NOEPERCUSSION 8 WORKS DEVICE 2 32 34 cus N VIC 33 RHBTHMZ PERCUSSION 2 ANDDEv|cE2 INVENTORS JAMES K. PULFER THEODORE H. SHEPERTYCKI TORNEYS.

ELECTRONIC MUSICAL INSTRUMENT WITH A PSEUDORANDOM PULSESEQUENCEGENERATOR BACKGROUND OF THE INVENTION This invention relates toapparatus for automatically producing complex rhythm patterns involvingoperation of a plurality of percussion devices in a pseudorandom manner.

For some time it has been possible to obtain percussion sounds on alarge musical instrument such as a theater organ. These sounds may beartificially generated or may be made with real percussion instruments.

More recently, it has been possible to produce rhythm devices which cancontrol the percussion sound to produce standard musical rhythms such aswaltz, fox-trot, etc. Arrangements of this type are disclosed in, forexample, the following U.S. Pats:

3.146.290 D.M. Park Aug. 25, I964 3,255,292 D.M. Park June 7, 19663,358,068 RJI. Campbell, Jr. Dec. 12, I967 3,383,452 D.M. Park et al.May l4, I968 These patents describe schemes for automatically selectingrhythm instruments such as drum, blocks, cymbals, etc. during prescribedtime intervals. None of the devices described in the patents is capableof automatically generating random or pseudorandom rhythm patterns. Atmost, they are only capable of producing repetitive patterns, which maybe manipulated by the artist. The standard rhythm patterns used arequite limited and soon become tiresome.

SUMMARY OF THE INVENTION The present invention provides a rhythmgenerator which may either lead or follow a performer, and which drivesa set of percussion instruments-either real or artificial. Unlike priorart arrangements, the present invention provides rhythm patterns whichare pseudorandom, i.e., the repetition period of the pattern is so longcompared to the memory of the listener or the duration of a musicalselection that it seems to be random. Prior art arrangements can thus beused to provide the normal rhythm accompaniment and the device accordingto the invention can be used to provide rhythm breaks. The net result ismuch more pleasant to listen to and approaches the rhythm patterns of ahuman percussion player. Thus the invention does not supplant the priorart arrangements but adds another dimension to the rhythm possibilitieswhen the musician selects it to perfonn its function. It adds, whenselected, a degree of unpredictability to the perfonnance of the rhythmaccompaniment which adds considerably to the quality of the resultantperformance.

The apparatus according to the invention comprises a source of clockpulses having an output which is applied to a clock input of apseudorandom pulse sequence generator having a large number of outputson which appear a large number of different combinations of outputpulses, each clock pulse effecting a change in the combination of pulsesappearing at the output. The outputs are connected via logic gates toinputs of a plurality of percussion devices whereby the percussiondevices are operated in pseudorandom manner at a tempo determined by thesource of clock pulses.

Following a brief description of the accompanying drawings, theinvention will be described in more detail.

BRIEF DESCRIPTION OF THE DRAWINGS ment using a free-running clock sothatthe musician must follow the percussion devices,

LII

FIG. 3 is a block diagram for explaining a third embodiment having asource of clock pulses which may be synchronized with amusical'instrument playedby a musician,

FIG. 4 is a block diagram of a form of pseudorandom pulse sequencegenerator which may be used in the present invention, and

FIGS. 5, 6 and 7 are block diagrams showing some possible ways ofconnecting the outputs of the pseudorandom pulse sequence generator to aplurality of percussion devices.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, aperformer (musician) Ill operates a musical instrument II which producesa sound output 13 and also produces clock pulses which are applied tothe rhythm box or pseudorandom pulse sequence generator 14 to cause thepattern of output pulses from the rhythm box to change. The musicalinstrument I! may be an organ and pulse generating means may beincorporated therein or associated therewith so that a pulse isgenerated each time a pedal is operated by the player. While the outputfrom rhythm box M is shown as a single line in FIG. 1 there are actuallymany output lines, as mentioned above and as will be explained below inconnection with FIG. 4. The output from rhythm box 14 is shown asfeeding a box 15 marked percussion which produces a sound output I6 butit should be understood that a plurality of percussion devices willgenerally be used in practice, e.g. various drums, cymbals, blocks, etc.

The sound outputs 13 and 16 are shown as being fed back to the performerII) which is, of course, what happens, i.e. the performer III hears bothsound outputs.

FIG. 2 shows a free-running pseudorandom rhythm box 14 drivingpercussion devices 15 to produce sound I6. Line 17 indicates that sound16 is heard by performer 10 who then plays instrument II to producesound 13. In this arrangement the performer tries to follow the tempoproduced by the rhythm box 14' although, of course, this tempo can beset as desired for different musical selections. The source of clockpulses in the FIG. 2 arrangement is not shown separately and may beassumed to be part of the rhythm box."

FIG. 3 shows an arrangement wherein a pulse source on a musicalinstrument 20 feeds one input of pulse comparison circuitry 21 havinganother input fed from the output of a source of clock pulses 22 whichis also fed to a pseudorandom pulse sequence generator 14 (rhythm box).Pulse comparison circuitry 21 compares the repetition rate of the pulsesfrom pulse source 20 with that of the pulses from the source of clockpulses 22 and if any difference is detected it produces an error signalon line 23 which adjusts the clock pulse frequency to make it agree withthe frequency from the pulse source on musical instrument 20. By thismeans the tempo of the clock pulses is synchronized with the tempo ofthe musical instrument. Pulse comparison devices are known and one isincluded in the arrangement described in the US. Pat. 3,243,494 of D. M.Park issued Mar. 29, 1966.

FIG. 4 is a block diagram of a pseudorandom pulse sequence generatorsuitable for use in the present invention. Other examples are given inan article in Electronic Instrument Digest," May June, 1966 by T. H.Shepertycki entitled Pseudorandom Signals Simplify Telemetry DistortionMeasurements. Obviously many types of pseudorandom pulse sequencegenerators are possible and the operation of the arrangement accordingto the invention is not dependent on any particular type. The mainconsideration is that the number of pulse combinations available shouldbe large so that the percussion devices appear to the listener to beoperated randomly.

The particular pseudorandom generator shown in FIG. 4 is a 10 stagem-length (maximal length) sequence generator. This type of sequencegenerator is described in some detail in Chapter III of Shift RegisterSequences" by Solomon W. Golomb published by Holden-Day Incorporated,I967, Library of Congress Catalog Card Number 66-17667. Briefly,however, it may be stated that it comprises 10 memory units (flip-.flops)connected together as a storage register. Every clock stage ti,the content of stage 8 is fed into stage 7, and so on. The input to thefirst flip-flop (stage El) in the register is obtained by combining theoutputs of at least two other flip-flops in the register in anexclusive-or adder. Proper choice of these feedback connections willensure that the lO-bit pattern appearing in the register will not berepeated until 2"-l=2 l==l ,023 clock pulses have been received. Aproper feedback connection is shown in FIG. 4 as being from the outputsof stages and 3 via the exclusive OR gate 40.

Outputs 0 to 9 are pulsed each time stages 0 to 9 are turned on by aclock pulse. Output I0 is pulsed each time there is a pulse on output 0or 3 (but not both) because of the exclusive OR gate 40. Similarly,output 21 is present each time output 4 or output 5 (but not both) ispresent because of exclusive OR gate il. It should now be obvious howoutputs 17 and 25 are derived. It should also be apparent that theremaining outputs (not shown) may be derived by further combining theoutputs shown, e.g. outputs 2 and 3, outputs 5 and 9, and so on.

While FIG. 4 illustrates an m-length (maximal length) pseudorandomgenerator it is not essential that the generator be an m-length one;this is, however, to be preferred to secure the maximum randomncss."

The register shown in FIG. 4 can only hold 1,024 distinct patterns. Theonly state not generated with this configuration is the all lls pattern.

The stages in FiG. 4 are numbered 0 to 9 from left to right although thefirst stage is stage 9. They could equally well be numbered from rightto left.

While the FIG. 4 arrangement uses exclusiveor circuits, other typescould use a combination of OR," AND, and perhaps exclusive-or circuits.

The outputs from the pseudorandom pulse sequence generator can be fed tothe percussion devices in many ways. For example, individual outputs canbe fed to individual percussion devices, or individual outputs can befed to more than one percussion device or individual outputs can becombined in other OR" or AND-gates and these outputs used to drive oneor more percussion devices. Some of these ways are shown in FIGS. 5, 6and 7.

FIG. 5 shows only 10 of the many outputs from the rhythm box It(pseudorandom pulse sequence generator). Here it is assumed thatpercussion device I is connected to output 1 of rhythm box It whilepercussion device 2 is connected to output 9. Percussion device I willplay when (and only when) a one is present on output I of rhythm box Mand percussion device 2 will play when (and only when) a one" is presenton output 9. Since the pulse sequence passing through the rhythm boxtakes L023 clock pulses to repeat, the sequence of "ones and zcroesf'passing each percussion device appears to be random."

Switching percussion device 1 to another output changes the delaybetween the pattern followed by devices 1 and 2. In the FIG. 5arrangement, the delay would be 91=8 units of time, or 8 clock pulses.

Obviously other percussion devices could be connected to the otheroutputs of the rhythm box 14. However, it would not be practical toconnect 1,023 percussion devices to the 1,023 outputs of the rhythm box;hence an arrangement as shown, in part, in FIG. 6 is preferred. Herelogic networks 28 and 29 are used to combine several outputs.

Percussion device ll will only operate when the correct pattern of onesand zeroes" appears at outputs 1-4- of the rhythm box I4. Depending onthe logic network selected, percussion device I may be operated moreoften than in the case of FIG. 5 (if the logic network is mostly OR"gates) or more seldom than in the case of FIG. 5 (if the logic networkis mostly AND"-gates As an example, percussion device 1 may be made tooperate if any only if the number 1,101 appears on outputs I 4. Sincethe probability of this happening is relatively small, percussion deviceI would be used only at rare intervals.

It seems reasonable that if many percussion devices are used say 26-thatsome should repeat fairly often to provide a basic through perhapsirregular beat, while otherssuch as cymbals or cow bells-should onlyplay at rare intervals.

Obviously the logic networks such as 28 and 29 may be made up of anysuitable gates such as OR," AND," "EX- CLUSIVE-OR, "NOR," NAND," etc.While FIG. 6 shows only two logic networks, quite a few more willgenerally be needed, depending on the number of percussion devices used.Also, while FIG. 6 shows four outputs of the rhythm box connected toeach logic network this is only exemplary; more or less than four couldbe used.

FIG. 7 is similar to FIG. 6 but shows some possible logic networks whichmay be used. Outputs 1 and 2 of rhythm box 14 are connected to AND-gate32 having its output connected to AND-gate 3d. Outputs 3 and 4 of rhythmbox 14 are connected to OR-gate 33 having its output also connected toAND-gate 34. It will readily be seen that percussion device I will beoperated it there are ones" on outputs 1 and 2 and 3 or outputs l and 2and 4. Percussion device 2 will only be operated only if there are"ones" on all of outputs 5, 6, 7 and 8 so that gate 35 is enabled.

It should be apparent from the foregoing that there exist virtually aninfinite number of possible ways of connecting the output leads of therhythm box to the percussion devices.

The invention could be implemented in many different ways --from asimple integrated circuit pseudorandom pulse sequence generator, whichwould be quite inexpensive, to a general purpose digital computer, whichwould be completely impractical in most applications.

What we claim as our invention is:

1. Apparatus for operating a plurality of percussion devices in apseudorandom manner to produce complex rhythm patterns, said apparatuscomprising a source of clock pulses having an output connected to aclock input of a pseudorandom pulse sequence generator, said generatorcomprising a large number of output tenninals and means to produce adifferent one of a large number of combinations of output pulses on saidoutput terminals in response to each clock pulse, and means connectingsaid output terminals to inputs of said plurality of percussion deviceswhereby said percussion devices are operated in pseudorandom manner at atempo determined by said source of clock pulses, wherein said outputterminals are divided into a plurality of groups of output terminals,each of said groups being connected to an associated logic networkhaving an output connected to an associated percussion device, andwherein said pseudorandom pulse sequence generator comprises a pluralityof cascaded flip-flops each of which receives said clock pulses so thatthe contents of each flip flop is shifted into the next adjacentflip-flop, the first of said flip-flops having an input obtained bycombining the outputs of at least two other of said flip-flops, theoutputs of said flip-flops being fed to an array of exclusive-orcircuits to derive further outputs.

2. Apparatus as claimed in claim 1 wherein there are 10 of saidflip-flops and 1,023 combinations of output pulses.

3. Apparatus for operating a plurality of percussion devices in apseudorandom manner to produce complex rhythm patterns, said apparatuscomprising a source of clock pulses having an output connected to aclock input of a pseudorandom pulse sequence generator, said generatorcomprising a large number of output terminals and means to produce adifferent one of a large number of combinations of output pulses on saidoutput terminals in response to each clock pulse, and means connectingsaid output terminals to inputs of said plurality of percussion deviceswhereby said percussion devices are operated in pseudorandom manner at atempo determined by said source of clock pulses, wherein said outputterminals are divided into a plurality of groups of output terminals,each of said groups being connected to an associated logic networkhaving an output connected to an associated percussion device, andwherein a manually actuated pulse source on a musical instrumentsupplies pulses to one input of pulse comparing circuitry havinga secondinput connected to the output of said source of clock pulses, said pulsecomparing circuitry producing an error voltage at its output if therepetition rate of the manually operated source differs from therepetition rate of the source of clock pulses, the output of the pulsecomparing circuitry being connected to a control input of said source ofclock pulses, said source of clock pulses being responsive to 5 an errorvoltage to adjust its pulse repetition rate to reduce the error voltageto zero.

is s v s e

1. Apparatus for operating a plurality of percussion devices in apseudorandom manner to produce complex rhythm patterns, said apparatusComprising a source of clock pulses having an output connected to aclock input of a pseudorandom pulse sequence generator, said generatorcomprising a large number of output terminals and means to produce adifferent one of a large number of combinations of output pulses on saidoutput terminals in response to each clock pulse, and means connectingsaid output terminals to inputs of said plurality of percussion deviceswhereby said percussion devices are operated in pseudorandom manner at atempo determined by said source of clock pulses, wherein said outputterminals are divided into a plurality of groups of output terminals,each of said groups being connected to an associated logic networkhaving an output connected to an associated percussion device, andwherein said pseudorandom pulse sequence generator comprises a pluralityof cascaded flip-flops each of which receives said clock pulses so thatthe contents of each flip-flop is shifted into the next adjacentflip-flop, the first of said flip-flops having an input obtained bycombining the outputs of at least two other of said flip-flops, theoutputs of said flip-flops being fed to an array of exclusive-orcircuits to derive further outputs.
 2. Apparatus as claimed in claim 1wherein there are 10 of said flip-flops and 1,023 combinations of outputpulses.
 3. Apparatus for operating a plurality of percussion devices ina pseudorandom manner to produce complex rhythm patterns, said apparatuscomprising a source of clock pulses having an output connected to aclock input of a pseudorandom pulse sequence generator, said generatorcomprising a large number of output terminals and means to produce adifferent one of a large number of combinations of output pulses on saidoutput terminals in response to each clock pulse, and means connectingsaid output terminals to inputs of said plurality of percussion deviceswhereby said percussion devices are operated in pseudorandom manner at atempo determined by said source of clock pulses, wherein said outputterminals are divided into a plurality of groups of output terminals,each of said groups being connected to an associated logic networkhaving an output connected to an associated percussion device, andwherein a manually actuated pulse source on a musical instrumentsupplies pulses to one input of pulse comparing circuitry having asecond input connected to the output of said source of clock pulses,said pulse comparing circuitry producing an error voltage at its outputif the repetition rate of the manually operated source differs from therepetition rate of the source of clock pulses, the output of the pulsecomparing circuitry being connected to a control input of said source ofclock pulses, said source of clock pulses being responsive to an errorvoltage to adjust its pulse repetition rate to reduce the error voltageto zero.